This invention generally relates to a testing instrument which detects defects in liquid crystal display base plates that are used for liquid crystal display panels, and the like.
When the area and the density of a liquid crystal display panel are increased to be suitable for use in a liquid crystal television, active matrix type liquid crystal display panels which utilize active matrix liquid crystal display base plates comprising multiple pixel element electrodes installed for each of the pixel elements arranged in lines, gate and source leads installed on each of the pixel element electrodes, and thin film transistors are preferred. At present, commercialization of these devices has been implemented with relatively small devices. Typically, liquid crystal display panels of this type are manufactured whereupon a transparent base plate, or the like, is placed over the active matrix liquid crystal display base plate via a spacer, then liquid crystal is sealed in the space between the active matrix liquid crystal display base plate and the transparent base plate.
Many liquid crystal televisions (TV's) currently in production employ liquid crystal display panels which have 250,000 to 500,000 pixel elements, and some with over 1,000,000 pixel elements.
To build such a large number of pixel elements and the corresponding number of leads on a base plate, various forming processes are performed inside a clean room where dust is kept at an extremely low level. When the width of the pixel element and the lead is extremely small, the presence of a trace amount of micro dust in the manufacturing environment is directly related to breakage or short-circuits of the pixel element electrodes, gate leads, and source leads. At present, up to 10 of those defects are accepted on an active matrix liquid crystal display base plate, but a product is considered defective if the number of defects exceeds this limit.
Using the present manufacturing technology, it is difficult to reduce these defects to keep within the allowable limit. Consequently, liquid crystal display panels with a large number of pixel elements have a significantly high number which are defective, causing the high prices of large liquid crystal panels.